Thanks for the nice explanation, MarkJ! I am getting new sails with vertical battens for my in-mast furler; these are supposed to work quite well.

My problem with the initial statement was the blanket "30%". First off, the lack of battens doesn affect performance on all points of sail. Secondly, close to 1/3 difference in performance between an in-mast furling main and a classically battened one even for courses close to the wind is exaggerated.

...

I replaced my sails with Neil Pryde PBF (vertical batten) sails in Oct 2008 and couldn't be happier - The mainsail shape is much better, the sail furles more easily (probably because of the stiffer sailcloth) and reefing is a piece of cake.

The Neil Pryde sails web page has a similar description to Mark's posting. According to them the traditional/furling sail area difference is 20% and PBF sails will gain back roughly half of it for you. Based on observing my sails, their statement is pretty accurate.

Another interesting point to note was following their sail trim directions - I must confess I'd never have considered reefing as early as they indicated for my Oceanis 461 - Got to try different a variety of different conditions during our recent Bahamasvacation and I have become a believer in following directions (forgive me Lord!... )

...just another quick note: I don't know how big of a hurry you are in for replacing your sails but most sailmakers have much more favorable (read: significantly discounted) prices during off season, as in Fall/Winter. You may also negotiate a better price at boat shows....

Consult a sailmaker, they will tell you that a lot of the mainsail drive comes from the roach... But what the heck, cruising boats dont have to be that concerned. Heck anything below 4 knots and I usually employed the Iron Reacher anyway!.....

Last month, while reading in my cockpit I noticed a guy up the mast and cutting up his "In mast furler" sail. Actually it looked like a rigger. The sail was jammed about half way out. The rigger was slowing climbing up the roach cutting and pulling the sail free. I don't know what happened. I do know it was a new boat, mabe owner didn't know the proper way to furl. Boy, it hurt watching someone take a knife to a big beautiful sail.
Erika

Last month, while reading in my cockpit I noticed a guy up the mast and cutting up his "In mast furler" sail. Actually it looked like a rigger. The sail was jammed about half way out. The rigger was slowing climbing up the roach cutting and pulling the sail free. I don't know what happened. I do know it was a new boat, mabe owner didn't know the proper way to furl. Boy, it hurt watching someone take a knife to a big beautiful sail.
Erika

I felt like taking a knife to my older sails a number of times... When the furling mains get older and the sailcloth is softer, they tend to not furl quite right and the 'furled' folds of the sail get sucked out through the mast opening with the 'unfurled' section of the sail, jamming in the opening in the process... In my case, this was aggrevated by the fact that the previous owner had somehow lost the tack attachment shackle (tied the tack with some thin line!), making it impossible/difficult to apply any halyard tension.

I was seriously doubting my decision to go with the furling main until I got the new sails - life has been wonderful since!...

It is a very good idea to read about some of the un-intuitive (sp? - is this a word? ) aspects of it as well - such as the use of the topping lift and the traveler (where exactly the boom needs to be in up/down and port/stb orientation during un/furling)

Location: Aboard, 8 years. Usually E.Coast of USA but right now we're in Havre de Grace, Maryland on C'peake Bay

Boat: Pearson 365 ketch, s/v Norne Gaest

Posts: 13

I do a lot of deliveries single-handed (mostly Hunters and Catalinas) and I really like in-mast furling. You can leave more sail out longer without reefing since you can reduce sail area fast. The trick is to reef the main when you are little off the wind so there is some tension on the sail. This help insure a tight wrap. Vertical battens help give you a better sail shape. I think a case could be made that two boats, one with slab reefing and one with in mast furling, that are sailing on a day with variable winds of 8 to 20 knots on C'peake Bay... the in-mast boat would 'get there' faster because the course could be held while furling where the 'slab-reefing' boat would have to head into the wind to reef (but, I'm no racer). From my perspective, in-mast furling is 'safety equipment'. It lets you have infinite reefing quickly with out anyone leaving the cockpit. This is especially true for us older sailors and those who do coastal cruising with a small crew.

"I felt like taking a knife to my older sails a number of times... When the furling mains get older and the sailcloth is softer, they tend to....."
Although my boat reputedly had a near new main, it had a patch point on it (probably from the in mast reefing from the look) I bought a brand new mainsail for mine and it still got wrapped up sometimes. Of couse it did it most often when you were the most out of control (you know, 30 knots of wind, lines everywhere, etc etc...) It worked best as noted above when you could crack off the wind slightly to tension the sail evenly along the luff. Unfortunately, when yo need things to work well is not at the end of a 10knot sail, but when you are out of control!